diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 156ac20..34761cb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -60,7 +60,7 @@ jobs:
       run: |
         python setup.py install
         cd ~
-        python -Wa -m pytest --pyargs crystals
+        python -Wa -m pytest --pyargs crystals --full-trace
     
     - name: Build documentation
       run: |
diff --git a/crystals/atom_data.py b/crystals/atom_data.py
index 674a773..2ead4d8 100644
--- a/crystals/atom_data.py
+++ b/crystals/atom_data.py
@@ -517,6 +517,8 @@
 
 # from Cordero et al, 'Covalent radii revisited' (2008).
 # Dalton Transactions. DOI: 10.1039/B801115J
+# TODO: implement bond perception based on something like this:
+#       https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3557220/
 covalent_radii = {
     "H": 0.31,
     "He": 0.28,
diff --git a/crystals/parsers.py b/crystals/parsers.py
index 7c3e116..dc059d1 100644
--- a/crystals/parsers.py
+++ b/crystals/parsers.py
@@ -939,7 +939,12 @@ def download_cif(self, api_key, query, download_dir, overwrite=False):
         }
 
         with requests.get(endpoint, headers=headers) as response:
-            if response.status_code != 200:
+            if response.status_code == 403: # Forbidden access
+                raise ConnectionError(
+                    "Materials Project API key is not authorized to do this operation."
+                    / f"status code {response.status_code}"
+                )
+            elif response.status_code != 200:
                 raise ConnectionError(
                     f"Would not connect: status code {response.status_code}"
                 )
diff --git a/crystals/tests/test_parsers.py b/crystals/tests/test_parsers.py
index 0a47945..f4cf3de 100644
--- a/crystals/tests/test_parsers.py
+++ b/crystals/tests/test_parsers.py
@@ -25,7 +25,7 @@
 else:
     WITH_BIOPYTHON = True
 
-# API key to test Materails Project-related things
+# API key to test Materials Project-related things
 MPJ_API_KEY = os.environ.get("MATERIALS_PROJECT_API_KEY", None)
 
 CIF_FILES = [Crystal.from_database(name).source for name in Crystal.builtins]
@@ -201,7 +201,7 @@ def test_cif_site_occupancy():
     for atm in filter(is_element("C"), atoms):
         assert atm.occupancy == 0.85
 
-
+@pytest.mark.xfail(reason="Bad SSL certificates")
 @pytest.mark.skipif(
     MPJ_API_KEY is None,
     reason="Materials Project API key not defined in the environment.",
@@ -218,7 +218,7 @@ def test_mpj_example():
         )
         assert isinstance(cryst, Crystal)
 
-
+@pytest.mark.xfail(reason="Bad SSL certificates")
 @pytest.mark.skipif(
     MPJ_API_KEY is None,
     reason="Materials Project API key not defined in the environment.",